超音速火焰喷涂金属陶瓷涂层与电镀硬铬在盐雾气氛下的腐蚀-磨损机制研究

study on tribological properties of HVOF cermet coatings as alternative to Cr-plating in artificial salt-fog atmosphere

摘要:

航空和海洋工程的关键部件在遭受磨损的同时受到海洋苛刻气氛的腐蚀破坏，而采用超音速火焰喷涂（HVOF）金属陶瓷涂层已成为一种新兴防护技术。为考察碳化物类金属陶瓷涂层的在海洋气氛下的抗腐蚀与抗磨损性能，采用超音速火焰喷涂技术制备了WC-10Co4Cr和Cr3C2-NiCr两种典型的金属陶瓷涂层，采用自制的盐雾喷射腐蚀-磨损装置，研究涂层的腐蚀-磨损行为，同时与传统的硬铬镀层作对比，并采用扫描电镜(SEM)、能谱分析(EDAX)等表征试样的腐蚀磨损形貌特征。结果显示，在干燥大气环境下铬镀层主要表现为黏着-磨损机制，Cr3C2-NiCr涂层同时表现出黏着-磨损与磨粒-磨损机制，而WC-10Co4Cr则表现为单纯的磨粒-磨损。施加盐雾气氛后，试样表面形成有液态膜，摩擦系数与磨损量均有所下降。盐雾气氛下增大摩擦副的载荷压力，Cr3C2-NiCr涂层的磨损量增加很快，而WC-10Co4Cr涂层的磨损机制发生转变，磨损量出现不增反降现象。

Abstract:

HVOF cermet coatings have been widely used in aviation and marine fields of key components. Those parts often serve in rigorous environment characterized with salt-fog atmosphere. In order to enhance the wear- and corrosion-resistance of those components, two kinds of cermet coating, that is WC-10Co4Cr and Cr3C2-NiCr coating, were prepared by HVOF and then their tribology properties were investigated by a reconstructive friction testing machine equipped with an artificial salt-fog spraying apparatus. As well as, similar research was performed on traditional chrome plating (Cr-plating) for contrasting. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to characterize the wear surface. The results indicated that various coatings exhibited different wear mechanisms. Cr-plating displayed mainly adhesive-wear mechanism, Cr3C2-NiCr coating displayed both adhesive-wear and abrasive-wear mechanism, while WC-10Co4Cr displayed mainly abrasive-wear mechanism. At the salt-fog atmosphere, liquid membrane was considered as a factor to reduce the friction-coefficient and wear-rate of the coatings. It was also indicatied that when the contacting pressure of the friction pair was increased, the wear-rate of Cr-plating and Cr3C2-NiCr coating are significantly enhanced, but that of WC-10Co4Cr coating is reduced at the opposite way. The phenomenon can ben ascribed to different transformation mechanism of abrasion for various coating at high contacting pressure.